This application claims the priority of German patent document 10 2005 003 582.5, filed Jan. 26, 2005, the disclosure of which is expressly incorporated by reference herein.
The invention is directed to a muffler for an exhaust gas system of an internal-combustion engine of a motor vehicle.
FIG. 5 of German Patent Document DE 38 35 079 A1 shows a muffler of the generic type, which has a single exhaust gas inlet and two exhaust gas tail pipes. The muffler is completely penetrated by a first flow pipe which has the single exhaust gas inlet as well as one of the exhaust gas tail pipes. A shut-off device (in the form of a so-called exhaust gas flap which can be operated by means of a swiveling mechanism) for shutting off and opening up the first flow pipe is arranged in the exhaust gas tail pipe, situated downstream of the muffler. A second flow pipe is arranged inside the muffler and extends by means of the second exhaust gas tail pipe out of the muffler.
When the shut-off device is opened, the exhaust gas flow of the internal-combustion engine enters via the exhaust gas inlet, and can be guided via the first flow pipe, unhindered to the exhaust gas tail pipe. When the shut-off device is closed, the exhaust gas flows out by way of a perforation in the first flow pipe arranged inside the muffler, penetrates a connection piece arranged in a dividing wall and enters by way of a perforation in the second flow path, and can thus be removed by way of the second exhaust gas tail pipe. The two perforations and the connection piece arranged in the dividing wall therefore form an overflow path between the first and the second flow pipe situated inside the muffler.
One object of the invention to provide a muffler of the initially mentioned type, whose function and the integration into an exhaust gas system are improved.
This and other objects and advantages are achieved by the muffler configuration according to the invention, in which exhaust gas noise exiting from the exhaust gas tail pipe is favorably influenced by the arrangement of the shut-off device upstream of the muffler. By positioning the shut-off device in front of the muffler according to the invention, a clear sound difference can be achieved when the exhaust gas produced by the internal-combustion engine is guided through the first or the second flow pipe. By means of the branching element, which connects the exhaust gas inlet with the first and second flow pipes, the muffler according to the invention can also be integrated in conventional exhaust gas systems and, as required, can also be retrofitted into an exhaust gas system without shut-off devices.
In one embodiment of the invention, it is advantageous that no separate branching element is required, because the catalyst housing is equipped with this branching element. It can therefore be provided according to a preferred embodiment that the catalyst housing has a front plate which forms the branching element. In this case, the front plate, for example, can have branching openings which are adjoined by the first and second flow pipes.
According to a further embodiment of the invention, the catalyst housing is fastened directly to the muffler, so that exhaust gas pipes, which are otherwise provided between the catalyst housing and the muffler, can be eliminated.
The catalyst housing can be situated at least partly inside the muffler, permitting a simple connection between the catalyst housing and the muffler. If at least the front plate of the catalyst housing is situated inside the muffler, it can form a wall of the muffler.
According to another embodiment of the invention, the shut-off device can advantageously be arranged outside the muffler, which permits a simple connection of the shut-off device with a drive provided for this purpose.
In a particularly preferred embodiment, the muffler has a cutout which accommodates the bypass section that has the shut-off device. In comparison to a conventional muffler without a shut-off device, no enlarged installation space is therefore required in the case of the muffler according to the invention.
If the overflow path has a muffling device, the sound of the muffler will differ further when the shut-off device is opened or closed. Particularly preferably, the muffling device may have a perforated dividing wall which is arranged inside the muffler.
In another preferred embodiment of the overflow path, when the shut-off device is opened, a chamber having a volume that is bounded by the first dividing wall, is coupled by way of the inlet to the first flow pipe. This arrangement favorably influences the sound of the muffler when the shut-off device is opened.
A second dividing wall can also be provided, to support the first and the second flow pipe inside the muffler.
If the second dividing wall has a perforated construction, another chamber, whose volume can be coupled to the first chamber, can be formed within the muffler, favorably influencing the muffling of the noise of the exhaust gas.
The muffler according to the invention can advantageously be connected with a continuing exhaust gas outlet which may also be provided for a conventional muffler without shut-off devices. Thus, an exhaust gas system in a modular construction can be provided, in which case the muffler with the shut-off device can easily be exchanged for a muffler without a shut-off device and vice-versa.
The modular construction is further developed if the catalyst housing, the muffler with the two flow pipes, the exhaust gas tail pipe and the shut-off device form a preassembled constructional unit, which can be inserted into the motor vehicle with the exhaust gas system.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.